Preparation of low bulk density sodium dichloroisocyanurate dihydrate

ABSTRACT

Process for producing a storage-stable, freeflowing, thermaldecomposition resistant, low bulk density sodium dichloroisocyanurate dihydrate by contacting a water-wet sodium dichloroisocyanurate dihydrate with a water miscible organic solvent and drying the solvent-wet material to remove the solvent from the material without removing the waters of hydration.

United States Patent 1191 1111 3,888,855

Berkowitz June 10, 1975 PREPARATION OF LOW BULK DENSITY 3,035,057 5/1962Symes 260/248 SODIUM DICHLOROISOCYANURATE 3,452,0l2 6/1969 Langenho'ffet al 260/248 DIHYDRATE 3,803,144 4/1974 Berkowitz 260/248 [75]Inventor: Sidney Berkowitz, Highland Park,

[73] Assignee: FMC Corporation, New York, NY.

[22] Filed: July 13, 1973 [21] Appl. N04 378,829

[52] US. Cl 260/248 C [51] Int. Cl C07d 55/38 [58] Field of Search260/248 C [56] References Cited UNITED STATES PATENTS 3,035,056 5/1962Symes 260/248 Primary ExaminerJ0hn M. Ford [5 7 ABSTRACT Process forproducing a storage-stable, freeflowing, thermal-decompositionresistant, low bulk density sodium dichloroisocyanurate dihydrate bycontacting a water-wet sodium dichloroisocyanurate dihydrate with awater miscible organic solvent and drying the solvent-wet material toremove the solvent from the material without removing the waters ofhydration.

6 Claims, N0 Drawings PREPARATION OF LOW BULK DENSITY SODIUlVIDICHLOROISOCYANURATE DIHYDRATE This invention relates to the productionof low bulk density sodium dichloroisocyanurate dihydrate from waterwetcrystals of sodium dichloroisocyanurate dihydrate feed materials.

Dichloroisocyanurates are well-known materials which are widely used asa source of available chlorine in solid bleaching, sanitizing anddetergent compositions. The sodium and potassium salts are the mostwidely used in laundering compositions because they are very soluble andeasily removed by rinsing. The sodium dichloroisocyanurate compounds areknown to exist in three forms, namely, the anhydrous form, themonohydrate (containing approximately 7.6% water of hydration byweight), and the dihydrate (containing approximately 141% water ofhydration by weight). See Symes, US. Pat. Nos. 3,035,056 and 3,035,057.

One prior art procedure for producing sodium dichloroisocyanuratedihydrate involves the chlorination of trisodiumi socyanurate withgaseous chlorine. The dihydrate solids produced by chlorination areseparated from the bulk of the aqueous phase by wellknown methods forseparating solids from liquids, and then dried to remove uncombinedwater to produce dry sodium dichloroisocyanurate. Dihydrates produced inthis manner have bulk densities of approximately 35 pounds/cubic foot or0.56 grams/cubic centimeter. These dihydrates are effective as a sourceof available chlorine when mixed with components of solid bleaching anddetergent compositions having the same bulk density. However, whenadmixed with components of a low bulk density or fluffy type bleachingor detergent formulation, uniform formulations are not obtained sincethe formulations segregate during storage or shipping. This segregationresults in non-homogeneous formulations which do not yield consistentsanitizing and- /or bleaching action.

One attempt to produce preparations of bleaching, sterilizing anddisinfecting compositions with varying bulk densities is disclosed byBrown et al in U.S. Pat. No. 3,293,188. Brown et al teach mixing adichlorocyanurate (in acid or salt form) with a synergistic carrieragent mixture of sodium tripolyphosphate and sodium sulfate decahydrate.This mixture is heated and cooled to form a slurry or plastic mass,which is then dried at high temperatures, approximately 95C andpulverized to form a powdered product with a low bulk density whosewater content can vary from 7 to 30%. The bulk density of the finalproduct is dependent upon the amount of water employed for combining thecarrier agent and the dichlorocyanurate. Moisture contents between andby weight form dense homogeneous products upon drying. As the moisturecontents are increased up to 50% by weight, compositions ofprogressively decreasing bulk densities are produced upon drying. Therange of the bulk densities for the compositions produced in this mannerare from 0.439 to 0.802 grams/cubic centimeter.

Brown et als use of high temperatures (95C) to dry their compositions,results in decomposition of the dichloroisocyanurate and in a productwherein the sodium dichloroisocyanurate component must be in theanhydrous and/or the monohydrate form. Such decomposition also resultsin lowering availab'lechlorinecontent of the product. While thepatentees state that their products are low bulk density materials,these products, when admixed with low bulk density or fluffy typebleaching or detergent formulations, become segregated during shippingand storage. Segregation results in formulations that fail to yieldconsistent sanitizing and/or bleaching action.

It is the object of my invention to produce a storagestable,free-flowing, thermal-decomposition resistant, low bulk density productwithout loss of available chlorine that will not cake, lump nordeliquesce when compounded and packaged, and which may be blended oradmixed with low bulk density or fluffy type disinfecting, bleaching ordetergent formulations.

I have discovered that a storage-stable, free-flowing,thermal-decomposition resistant, low bulk density sodiumdichloroisocyanurate dihydrate can be prepared from waterwet crystals ofsodium dichloroisocyanurate dihydrate by contacting the water-wetdihydrate crystals with a water miscible organic solvent, then dryingthe solvent containing material at temperatures below about 48C toremove the contacting liquid and not the waters of hydration. Quiteunexpectedly, a sodium dichloroisocyanurate dihydrate product isproduced having a bulk density at least four times lighter than sodiumdichloroisocyanurate dihydrate prepared in the conventional manner.

The term low bulk density sodium dichloroisocyanurate dihydrate used todefine the product of the invention means a sodium dichloroisocyanuratedihydrate having a bulk density of about 0.1 to about 0.3 grams/cubiccentimeter.

Sodium dichloroisocyanurate dihydrate may be produced by anyconventional manner and used in the process of the invention. Thedihydrate feed material may be in either dry or water-wet form. Whenemploying dry dihydrate, it is advantageous to dissolve the dry crystalsin water in order to dissolve the crystalline agglomerates. The solutioncontaining the dissolved crystals is then evaporated and/or cooled, e.g.to below 12C, to reform the crystals. The reformed crystals are thenseparated from the aqueous solution, mixed with the contacting liquid,and dried.

Precipitated sodium dichloroisocyanurate dihydrate produced by eitherconventional means or by dissolving crystalline agglomerates discussedabove may be separated from the bulk of the aqueous reaction solution byany well-known means, such as by filtration, centrifugation, decantationor the like.

The treatment with the contacting liquid is carried out by adding theorganic solvent to the precipitate and contacting and mixing theprecipitate with the organic solvent. The organic solvent should beadded almost immediately to the separated precipitate to remove anyresidual reaction solution. Such contacting, results in the formation oflow bulk density crystals which are approximately 3 X microns in size.If the mother liquor is allowed to remain on the crystals duringseparation, the crystals will break and agglomerate, resulting incrystals of higher bulk densities that are about 6 X 30 microns in size.If the precipitate is allowed to dry, it will cake in such a manner thatcomplete contact with the solvent will be impossible.

The contacting liquid may be added completely at one time or added insmall portions, each portion being drained completely before the nextone is added. Generally, it is more efficient to employ two smallportions of contacting liquid than one portion of the same total volume.When employing two or more portions of contacting liquid, the contactingliquid may be reused with fresh contacting liquid. Thorough mixing ofthe precipitate and contacting liquid is necessary if the full benefitsof the invention are to be realized.

The contacting liquid used for contacting the waterwet dihydratecrystals must be an organic solvent that is miscible with water. Theboiling point of the solvent should be relatively low, that is less thanabout 48C, so that drying temperatures below about 48C will remove thesolvent from the dihydrate but not the waters of hydration. If anorganic solvent having a boiling point about 48C is desired, drying mustbe conducted under vacuum to assure drying at below 48C. The solventshould also be chemically inert in the presence of the dihydrate.Examples of organic solvents which may be employed in my invention areacetone, methanol, tetrahydrofuran, and acetonitrile.

After the dihydrate crystals have been thoroughly mixed with thecontacting liquid, the dihydrate crystals are dried. Drying may becarried out by any known manner, such as by a warm air stream or in avacuum oven.

Drying temperatures below about 48C are employed, and preferably between25 and 35C. Temperatures slightly above 48C may be employed if losses ofminor amountsof water of hydration can be tolerated. Temperaturesaboveabout 66C are avoided in order to prevent the formation of the anhydroussalt. Drying temperatures are employed which will remove the organicsolvent retained by the precipitate but which will not remove the sodiumdiehloroisocyanurate waters of hydration.

The low bulk'density sodium diehloroisocyanurate crystals of theinvention have an average size of 3 X 180 microns and a bulk density ofabout 0.1 to about 0.3 grams/cubic centimeter, preferably about 0.13 toabout 0.25 grams/cubic centimeter. A particularly preferred bulk densityis on the order of 0.13 grams/cubic centimeter. Upon heating, bothwaters of hydration are lost in one step at temperatures between 48 and66C. These low bulk density crystals have the same excellentstorage-stability and free-flowing properties as the conventionallyprepared sodium diehloroisocyanurate dihydrate. The inventive crystalsare also resistant to thermal decomposition, a property which is anespecial advantage of the dihydrate material. Conventionally preparedsodium diehloroisocyanurate dihydrate crystals are in agglomerated formand have an approximate size of 6 X 30 microns and bulk densities above0.56 grams/cubic centimeter. Upon heating, waters of hydration arereleased in two steps. The first water of hydration is removed attemperatures between 65 and 70C. The second water of hydration isremoved at temperatures between 105 and 1 10C. 1

The following examples are given not by way of limitation, but merely asdescriptive of the invention.

EXAMPLE l-A Prior Art Preparation of Sodium DichloroisocyanurateDihydrate A by weight aqueous slurry of diehloroisocyanuric acid wasprepared and fed into a reactor. A 50% sodium hydroxide solution wasprepared and was simultaneously fed into the same reactor at asufficient rate to maintain the pH at 6.8. The temperature of thereaction mixture was maintained between 20 and 25C by a water cooledheat exchanger. The resulting slurry containing precipitated sodiumdiehloroisocyanurate dihydrate was filtered through a medium porosityfunnel to separate the salt from the aqueous medium. The separated saltwas then gently dried at about 40C in a warm air stream forapproximately 24 hours. The resultant product was a free-flowing, whitecrystalline sodium diehloroisocyanurate dihydrate material. Availablechlorine was assayed at 55.2%, theoretical 55.4%. The dihydrates bulkdensity was 35 pounds/cubic foot (0.56 grams/cubic centimeter).

EXAMPLE l-B Process of the Invention Sodium diehloroisocyanuratedihydrate was produced and recovered according to Example l except thatno drying step was carried out. Immediately after filtration, thewater-wet dihydrate crystals were thoroughly contacted and mixed withacetone. The acetone-wet salt product was then dried at about 30C in awarm air stream for approximately 24 hours. The resultant product was afluffy, free-flowing, white crystalline product identified as sodiumdiehloroisocyanurate dihydrate material having an available chlorineassay of 55.2%; theoretical 55.4%. The dihydrate had a bulk density of8.1 pounds/cubic foot (0.13 grams/cubic centimeter).

EXAMPLE 2 Horizontal Flame Propagation Test Samples from Examples l-Aand l-B were tested according to Procedure Rl7593 of the US. Bureau ofMines. The samples were placed in a l X 2 X 7 inch bed and heated at oneend with a propane torch. The rate of horizontal flame propagation wastimed and measured. The products from Examples l-A and l-B showed noflame propagation and could not be ignited.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications are intended to be included within the scope of thefollowing claims.

What is claimed is:

1. A process for the production of a storage-stable, free-flowing,thermal-decomposition resistant, low bulk density sodiumdiehloroisocyanurate dihydrate which comprises contacting water-wetsodium dichloroisocyanurate dihydrate with a water miscible organicsolvent, drying the solvent treated sodium diehloroisocyanurate at atemperature less than about 48C to remove the organic solvent and notthe waters of hydration, and recovering a low bulk density, sodiumdichloroisocyanurate dihydrate having a bulk density of about 0.1 toabout 0.3 grams/cubic centimeter.

2. The process of claim 1 wherein the water miscible organic solvent isacetone.

3. The process of claim 2 wherein the drying temperature is between 25and 35C.

4. Sodium diehloroisocyanurate dihydrate having a bulk density of about0.1 to about 0.3 grams/cubic centimeter.

5.. Sodium diehloroisocyanurate dihydrate having a bulk density of about0.13 to about 0.25 grams/cubic centimeter.

6. Sodium diehloroisocyanurate dihydrate having a bulk density of 0.13grams/cubic centimeter.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENTNO.3,888,855

DATED June 10, 1975 lNVENTOR(fi) Sidney Berkowitz It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:'

Abstract, line 1, "freeflowing" should read free-flow'ing-..

Column 1, line 6, "waterwet" should read --waterwet-.

Column 2, line 17, "waterwet" should read --water-wet-.

Column 3, line 13, "about" should read abo\ re--.

V Signed and Scaicd this eighth Day of June 1976 {SEAL} RUTH C. MASON C.MARSHALL DANN Arresting 0mm (mnmiuhmn ofParem: and Trademark:

1. A PROCESS FOR THE PRODUCTION OF A STORAGE-STABLE, FREEFLOWING, THERMAL-DECOMPOSITION RESISTANT, LOW BULK DENSITY SODIUM DICHLOROISOCYANURATE DIHYDRATE WHICH COMPRISE CONSITACTING WATER-WET SODIUM DICHLOROISOCYANURATE DIHYDRATE WITH A WATER MISCIBLE ORGANIC SOLVENT, DRYING THE SOLVENT TREATED SODIUM DICHLOROISOCYANURATE AT A TEMPERTURE LESS THAN ABOUT 4(*C TO REMOVE THE ORGANIC SOLVENT AND NOT THE WATERS OF HYDRTION, AND RECOVERNG A LOW BULK DENSITY, SODIUM DICHLOROISOCYANURATE DIHYDRATE HAVING A BULK DENSITY OF ABOUT 0.1 TO ABOUT 0.3 GRMS/CUBIC CENTIMETER.
 2. The process of claim 1 wherein the water miscible organic solvent is acetone.
 3. The process of claim 2 wherein the drying temperature is between 25* and 35*C.
 4. Sodium dichloroisocyanurate dihydrate having a bulk density of about 0.1 to about 0.3 grams/cubic centimeter. 5.. Sodium dichloroisocyanurate dihydrate having a bulk density of about 0.13 to about 0.25 grams/cubic centimeter.
 6. Sodium dichloroisocyanurate dihydrate having a bulk density of 0.13 grams/cubic centimeter. 